* Temperature assumed in calibration of scale. It was mentioned at the outset that dwarf stars appear to be at a higher temperature than giants of the same spectral class. The following table summarizes the differences in temperature, as compiled by Seares.[56] TABLE VII Class Effective Temperature Giant Dwarf 6080° 6080° 5300 5770 4610 5500 3860 4880 3270 4120 3080 3330 [Pg 32] A more detailed list of giant and dwarf temperatures was compiled in 1922 by Hertzsprung[57] from all the material then available. The tabulation that follows contains his values for (the “reciprocal temperature,” where is 14,600), and the corresponding absolute temperature, in degrees centigrade. TABLE VIII Mt. W. Class Giant Dwarf Temperature Giant Temperature Dwarf 2.00 7300° 2.16 6770 2.08 6990 2.26 6460 2.30 6350 2.11 6920 2.30 6350 2.29 6370 2.34 6240 2.36 6190 2.48 5880 2.30 2.51 6340° 5810 2.45 5970 2.71 5100 2.83 2.62 5170 5580 2.92 2.68 5020 5440 2.92 2.64 5020 5530 3.15 4730 3.09 4820 3.15 4730 3.25 2.76 4480 5300 3.20 4560 3.29 4430 3.39 3.03 4300 4840 3.48 3.11 4180 4700 3.50 3.05 4160 4790 3.54 4130 3.83 3810 3.86 3870 4.14 3530 4.33 3370 4.36 3350 4.35 3360 4.49 3250 4.45 3280 3.93 3720 [Pg 33] The difference in temperature between giant and dwarf stars of the same spectral class is clearly shown in the foregoing tables. The relation of absolute magnitude to effective temperature within a given class must be regarded as definitely established by observation. The temperatures for the cooler giant stars in both these lists are somewhat lower than those given for the corresponding classes in Table V. The temperature of , for instance, is placed nearer to 4000° than to 4500°. The fact that the sun, a typical dwarf, has an effective temperature of 5600° seems to favor these lower values. TABLE IX Class Temperature Class Temperature 3000° 9000° 3000 10000 3500 13500 4000 15000 5000 17000 5600 18000 7000 20000 7500 25000 8400 35000 In concluding the summary of stellar temperatures, the ionization temperature scale is given in the foregoing table. The discussion on which the table is based is contained in Chapters VI to IX, and it is merely placed here for comparison with the preceding tabulations. FOOTNOTES: [43] Eddington, Zeit. f. Phys., 7, 351, 1921. [44] Phil. Trans., 223A, 201, 1922. [45] Chapter IX, p. 136. [46] Chapter XIV, p. 195. [47] Wilsing and Scheiner, Pots. Pub., 24, No. 74, 1919. [48] Pots. Pub., 24, No. 76, 1920. [49] H. A., 76, 107, 1916. [50] A.N., 193, 356, 1912. [51] A. N., 218, 210, 1923; ibid., 219, 22 and 354, 1923; Die Strahlung der Sterne, Berlin, 1924. [52] Rep., Smithsonian Ap. Obs., 1924. [53] Pop. Ast., 21, 105, 1923. [54] M. N. R. A. S., 85, 212, 1925. [55] Pub. Dom. Ap. Obs., 2, 12, 1923. [56] Ap. J., 55, 202, 1922. [57] Lei. An., 14, 1, 1922. [Pg 34] CHAPTER III PRESSURES IN STELLAR ATMOSPHERES